Vacuum processing apparatus and operating method therefor

ABSTRACT

This invention relates to a vacuum processing apparatus having vacuum processing chambers the insides of which must be dry cleaned, and to a method of operating such an apparatus. When the vacuum processing chambers are dry-cleaned, dummy substrates are transferred into the vacuum processing chamber by substrates conveyor means from dummy substrate storage means which is disposed in the air atmosphere together with storage means for storing substrates to be processed, and the inside of the vacuum processing chamber is dry-cleaned by generating a plasma. The dummy substrate is returned to the dummy substrate a storage means after dry cleaning is completed. Accordingly, any specific mechanism for only the cleaning purpose is not necessary and the construction of the apparatus can be made simple. Furthermore, the dummy substrates used for dry cleaning and the substrates to be processed do not coexist, contamination of the substrates to be processed due to dust and remaining gas can be prevented and the production yield can be high.

[0001] This application is a Continuation application of Ser. No.08/882,731, filed Jun. 26, 1997, which is a Divisional application ofSer. No. 08/593,870, filed Jan. 30, 1996, which is a Continuingapplication of Ser. No. 08/443,039, filed May 17, 1995, which is aDivisional application of Ser. No. 08/302,443, filed Sep. 9, 1994, whichis a Continuing application of Ser. No. 08/096,256, filed Jul. 26, 1993,which is a Continuing application of Ser. No. 07/751,951, filed Aug. 29,1991.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] This invention relates to a vacuum processing apparatus andoperating method therefore. More specifically, the present inventionrelates to a vacuum processing apparatus having vacuum processingchambers the inside of which must be cleaned, and its operating method.

[0004] 2. Description of the Prior Art

[0005] In a vacuum processing apparatus such as a dry etching apparatus,a CVD apparatus or a sputtering apparatus, a predetermined number ofsubstrates to be treated are stored as one unit (which is generallyreferred to as a “lot”) in a substrate cassette and are loaded in theapparatus. The substrates after being processed are likewise stored inthe same unit in the substrate cassette and are recovered. This is anordinary method of operating these apparatuses to improve theproductivity.

[0006] In such a vacuum processing apparatus described above,particularly in an apparatus which utilizes a reaction by an active gas,as typified by a dry etching apparatus and a CVD apparatus, reactionproducts adhere to and are deposited on a vacuum processing chamber withthe progress of processing. For this reason, problems such asdegradation of vacuum performance, the increase of dust, the drop of thelevels of optical monitoring signals occur. To solve these problems,conventionally the insides of the vacuum processing chambers are cleanedperiodically. Cleaning operations include so-called “wet cleaning” whichis wiping-off of the adhering matters by use of an organic solvent,etc., and so-called “dry cleaning” in which an active gas or plasma isused for decomposing adhering matters. Dry cleaning is superior from theaspect of the working factor and efficiency. These features of the drycleaning have become essential with the progress in automation ofproduction lines.

[0007] An example of vacuum processing apparatuses having such a drycleaning function is disclosed in Japanese Utility Model Laid-Open No127125/1988. This apparatus includes a preliminary vacuum chamber forintroducing wafers to be treated into a processing chamber from anatmospheric side to a vacuum side, which is disposed adjacent to theprocessing chamber through a gate valve, dummy wafers are loaded in thepreliminary vacuum chamber and are transferred into the processingchamber by exclusive conveyor means before the processing chamber issubjected to dry cleaning, and the dummy wafer is returned to the vacuumpreparatory chamber by the conveyor means after dry cleaning iscompleted.

SUMMARY OF THE INVENTION

[0008] In the prior art technology described above, the structure of thevacuum processing apparatus is not much considered. The preliminaryvacuum chamber for storing the dummy wafers must have a large capacity,the exclusive conveyor means is necessary for transferring the dummywafers and thus, the apparatus is complicated in structure.

[0009] Dummy wafers used for plasma cleaning are again returned to thepreliminary vacuum chamber and are made to stand by. In this instance,reaction products generated during plasma cleaning and residual gas usedfor plasma cleaning adhere on the used dummy wafers. Thereafter, normalprocessing for wafers is resumed. Therefore, the used dummy wafers andunprocessed wafers exist in mixture inside the preliminary vacuumchamber and this state is not desirable from the aspect of contaminationof unprocessed wafers.

[0010] The present invention provides a vacuum processing apparatuswhich solves the problems described above, is simple in structure,prevents contamination of unprocessed substrates and accomplishes a highproduction yield. A vacuum processing apparatus having vacuum processingchambers the insides of which are dry-cleaned after substrates to betreated are processed in vacuum is provided with first storage means forstoring substrates to be treated, second storage means for storing dummysubstrates, the first and second storage means being disposed in theair, conveyor means for transferring the substrates to be processedbetween the first storage means and the vacuum processing chambers andfor transferring the dummy substrates between the second storage meansand the vacuum processing chambers, and control means for controllingthe conveyor means so as to transfer the dummy substrates between thesecond storage means and the vacuum processing chambers before and afterdry cleaning of the vacuum processing chambers. A method of operating avacuum processing apparatus having vacuum processing chambers theinsides of which are dry-cleaned after substrates to be processed areprocessed in vacuum comprises the steps of disposing first storage meansfor storing the substrates to be processed together with second storagemeans for storing dummy substrates in the air atmosphere, transferringthe substrates to be processed between the first storage means and thevacuum processing chambers and vacuum-processing the substrates to beprocessed, and transferring the dummy substrates between the secondstorage means and the vacuum processing chambers before and afterdry-cleaning of the vacuum processing chambers.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1 is a plan view of a dry etching apparatus as an embodimentof a vacuum processing apparatus in accordance with the presentinvention; and

[0012]FIG. 2 is a vertical sectional view taken along line 1-I of FIG.1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] As substrates to be processed are processed in a vacuumprocessing apparatus, reaction products adhere to and are deposited invacuum processing chambers. The reaction products adhering to anddeposited in the vacuum processing chambers are removed by disposingdummy wafers inside the vacuum processing chambers and by conductingdry-cleaning. To carry out dry cleaning, the timings of dry cleaning ofthe vacuum processing chambers are determined and during or after theprocessing of a predetermined number of substrates to be processed,dummy substrates are conveyed by substrate conveyor means from dummysubstrate storage means disposed in the air atmosphere together withprocessed substrate storage means, and are then disposed inside thevacuum processing chambers. After the dummy substrates are thusdisposed, a plasma is generated inside each of the vacuum processingchambers to execute dry-cleaning inside the vacuum processing chamber.After dry-cleaning inside the vacuum processing chambers is completed,the dummy substrates are returned from the vacuum processing chambers tothe dummy substrate storage means by the substrate conveyor means. Inthis manner, a preliminary vacuum chamber and an exclusive transfermechanism both necessary in prior art techniques become unnecessary, andthe apparatus structure gets simplified. The dummy substrates used forthe dry-cleaning and the substrates to be processed do not co-existinside the same chamber, so that contamination of substrates to beprocessed due to dust and remaining gas is prevented and a highproduction yield can be achieved.

[0014] Hereinafter, an embodiment of the present invention will beexplained with reference to FIGS. 1 and 2.

[0015]FIGS. 1 and 2 show a vacuum processing apparatus of the presentinvention which is, in this case, a dry-etching apparatus for etchingwafers, i.e., substrates to be processed by plasma.

[0016] Cassette tables 2 a to 2 c are disposed in an L-shape in thiscase in positions such that they can be loaded into and unloaded fromthe apparatus without changing their positions and postures. In otherwords, the cassettes 1 a to 1 c are fixed always in predeterminedpositions on a substantially horizontal plane, while the cassette tables2 a and 2 b are disposed adjacent to and in parallel with each other onone of the sides of the L-shape. The cassette table 2 c is disposed onthe other side of the L-shape. The cassettes 1 a and 1 b are for storingunprocessed wafers and for recovering the processed wafers. They canstore a plurality (usually 25) of wafers 20 as the substrates to betreated. The cassette 1 c in this case is for storing the dummy wafersfor effecting dry-cleaning using plasma (hereinafter referred to as“plasma-cleaning”) and recovering the dummy wafers afterplasma-cleaning. It can store a plurality of (usually twenty-fivepieces) dummy wafers 30.

[0017] A load lock chamber 5 and unload lock chamber 6 are so disposedas to face the cassette tables 2 a and 2 b, and a conveyor 13 isdisposed between the cassette tables 2 a, 2 b and the load lock chamber5 and the unload lock chamber 6. The load lock chamber 5 is equippedwith an evacuating device 3 and a gas introduction device 4, and canload unprocessed wafers in the vacuum apparatus through a gate valve 12a. The unload lock chamber 6 is similarly equipped with the evacuatingdevice 3 and the gas introduction device 4, and can take out processedwafers to the atmosphere through a gate valve 12 d. The conveyor 13 isequipped with a robot having X, Y, Z and θ axes, which operates so as todeliver and receive the wafers 20 between the cassettes 1 a, 1 b and theload lock and unload lock chambers 5 and 6 and the dummy wafers 30between the cassette 1 c and the load lock and unload lock chambers 5and 6.

[0018] The load lock chamber 5 and the unload lock chamber 6 areconnected to a transfer chamber 16 through the gate valves 12 b and 12c. The transfer chamber 16 is rectangular, in this case, and etchingchambers 11 a, 11 b and 11 c are disposed on the three side walls of thetransfer chamber 16 through gate valves 15 a, 15 b and 15 c,respectively. A conveyor 14 capable of delivering the wafers 20 or thedummy wafers 30 from the load lock chamber 5 to the etching chambers 11a, 11 b, 11 c and of delivering them from the chambers 11 a, 11 b, 11 cto the unload lock chamber 6 is disposed inside the transfer chamber 16.The transfer chamber 16 is equipped with an evacuating device 17 capableof independent evacuation.

[0019] The etching chambers 11 a, 11 b, 11 c have the same structure andcan make the same processing. The explanation will be given on theetching chamber 11 b by way of example. The etching chamber 11 b has asample table 8 b for placing the wafers 20 thereon, and a dischargechamber is so provided as to define a discharge portion 7 b above thesample table 8 b. The etching chamber 11 b includes a gas introductiondevice 10 b for introducing a processing gas in the discharge portion 7b and an evacuating device 9 b for decreasing the internal pressure ofthe etching chamber 11 b to a predetermined pressure. The etchingchamber 11 b further includes generation means for generating amicrowave and a magnetic field for converting processing gas in thedischarge portion 7 b to plasma.

[0020] A sensor 18 for measuring the intensity of plasma light isdisposed at an upper part of the etching chamber. The measured value ofthe sensor 13 is inputted to a controller 19. The controller 19 comparesthe measured value from the sensor 18 with a predetermined one anddetermines the timing of cleaning inside the etching chamber. Thecontroller 19 controls the conveyors 13 and 14 to control the transferof the dummy wafers 30 between the cassette 1 c and the etching chambers11 a to 11 c.

[0021] In a vacuum processing apparatus having the constructiondescribed above, the cassettes 1 a, 1 b storing unprocessed wafers arefirst placed onto the cassette tables 2 a, 2 b by a line transfer robotwhich operates on the basis of the data sent from a host controlapparatus, or by an operator. On the other hand, the cassette 1 cstoring the dummy wafers is placed on the cassette table 2 c. The vacuumprocessing apparatus executes the wafer processing or plasma cleaning onthe basis of recognition by itself of the production data provided onthe cassettes 1 a to 1 c, of the data sent from the host controlapparatus, or of the command inputted by an operator.

[0022] For instance, the wafers 20 are sequentially loaded in the orderfrom above into the etching chambers 11 a, 11 b, 11 c by the conveyors13 and 14, and are etched. The etched wafers are stored in theiroriginal positions inside the cassette 1 a by the conveyors 14 and 13.In this case, from the start to the end of the operation, withoutchanging the position and posture of the cassettes, the unprocessedwafers are taken out from the cassettes and are returned in theiroriginal positions where the wafers have been stored, and are storedthere. In this manner, the apparatus can easily cope with automation ofthe production line, contamination of the wafers due to dust can bereduced and high production efficiency and high production yield canthus be accomplished.

[0023] As etching is repeated, the reaction products adhere to and aredeposited on the inner wall of the etching chambers 11 a to 11 c.Therefore, the original state must be recovered by removing the adheringmatters by plasma cleaning The controller 19 judges the timing of thisplasma cleaning. In this case, a portion through which the plasma lightpasses is provided in each of the etching chambers 11 a to 11 c. Thesensor 18 measures the intensity of the plasma light passing throughthis portion and when the measured value reaches a predetermined one,the start timing of plasma cleaning is judged. Alternatively, the timingof plasma cleaning may be judged by counting the number of wafersprocessed in each etching chamber by the controller 19 and judging thetiming when this value reaches a predetermined value. The actual timingof plasma cleaning that is carried out may be during a processing of apredetermined number of wafers in the cassette 1 a or 1 b, after theprocessing of all the wafers 20 in a cassette is completed and beforethe processing of wafers in the next cassette.

[0024] Plasma cleaning is carried out in the following sequence. In thiscase, the explanation will be given about a case where the etchingchambers 11 a to 11 c are subjected to plasma cleaning by using threedummy wafers 30 among the dummy wafers 30 (twenty-five dummy wafers arestored in this case) stored in the cassette 1 c.

[0025] Dummy wafers 30 which are stored in the cassette 1 c and are notused yet or can be used because the number of times of use for plasmacleaning is below a predetermined one are drawn by the conveyor 13. Atthis time, dummy waters 30 stored in any position in the cassette 1 cmay be used but in this case, the position numbers of the dummy wafersin the cassette and their number of times of use are stored in thecontroller 19, and accordingly dummy wafers having smaller numbers oftimes of use are drawn preferentially. Then, the dummy wafers 30 areloaded in the load lock chamber 5 disposed on the opposite side to thecassette 1 a by the conveyor 13 through the gate valve 12 a in the sameway as the transfer at the time of etching of wafers 20. After the gatevalve 12 a is closed, the load lock chamber 5 is evacuated to apredetermined pressure by the vacuum exhaust device 3 and then the gatevalves 12 b and 15 a are opened. The dummy wafers 30 are transferred bythe conveyor 14 from the load lock chamber 5 to the etching chamber 11 athrough the transfer chamber 16 and are placed on the sample table 8 a.After the gate valve 15 a is closed, plasma cleaning is carried out inthe etching chamber 11 a in which the dummy wafers 30 are disposed,under a predetermined condition.

[0026] In the interim, the gate valves 12 a, 12 b are closed and thepressure of the load lock chamber 5 is returned to the atmosphericpressure by the gas introduction device 4. Next, the gate valve 12 a isopened and the second dummy wafer 30 is loaded in the load lock chamber5 by the conveyor 13 in the same way as the first dummy wafer 30, andevacuation is effected again by the evacuating device 3 to apredetermined pressure after closing the gate valve 12 a. Thereafter,the gate valves 12 b and 15 b are opened and the second dummy wafer 30is transferred from the load lock chamber 5 to the etching chamber 11 bthrough the transfer chamber 16 by the conveyor 14. Plasma cleaning isstarted after the gate valve 15 b is closed.

[0027] In the interim, the third dummy wafer 30 is transferred into theetching chamber 11 c in the same way as the second dummy wafer 30 andplasma cleaning is carried out.

[0028] After plasma cleaning is completed in the etching chamber 11 a inwhich the first dummy wafer 20 is placed, the gate valves 15 a and 12 care opened. The used dummy wafer 30 is transferred from the etchingchamber 11 a to the unload lock chamber 6 by the conveyor 14. Then, thegate valve 12 c is closed. After the pressure of the unload lock chamber6 is returned to the atmospheric pressure by the gas introduction device4, the gate valve 12 d is opened. The used dummy wafer 30 transferred tothe unload lock chamber 6 is taken out in the air by the conveyor 13through the gate valve 12 d and is returned to its original position inthe cassette 1 c in which it is stored at the start.

[0029] When plasma cleaning of the etching chambers 11 b and 11 c iscompleted, the second and third dummy wafers 20 are returned to theiroriginal positions in the cassette 1 c.

[0030] In this way, the used dummy wafers 30 are returned to theiroriginal positions in the cassette 1 c and the dummy wafers 30 arealways stocked in the cassette 1 c. When all the dummy wafers 30 in thecassette 1 c are used for plasma cleaning or when the numbers of timesof use of the wafers 30 reach the predetermined ones after therepetition of use, the dummy wafers 30 are replaced as a whole togetherwith the cassette 1 c. The timing of this replacement of the cassette ismanaged by the controller 19 and the replacement is instructed to thehost control apparatus for controlling the line transfer robot or to theoperator.

[0031] Although the explanation given above deals with the case wherethe etching chambers 11 a to 11 c are continuously plasma-cleaned by theuse of three dummy wafers 30 among the dummy wafers 30 in the cassette 1c, other processing methods may be employed, as well.

[0032] For example, the etching chambers 11 a to 11 c are sequentiallyplasma-cleaned by the use of one dummy wafer 30. In the case of suchplasma cleaning, unprocessed wafers 20 can be etched in etching chambersother than the one subjected to plasma cleaning, and plasma cleaning canthus be carried out without interrupting etching.

[0033] If the processing chambers are different, for example, there arean etching chamber, a post-processing chamber and a film-formationchamber, and wafers are sequentially processed while passing througheach of these processing chambers, each of the processing chambers canbe subjected appropriately to plasma cleaning by sending dummy wafers 30during the processing of the wafers 20 which are stored in the cassette1 a or 2 a and drawn and sent sequentially, by passing merely the dummywafers 30 through the processing chambers for which plasma cleaning isnot necessary, and by executing plasma cleaning only when the dummywafers 30 reach the processing chambers which need plasma cleaning.

[0034] According to the embodiment described above, the cassette storingthe dummy wafers and the cassettes storing the wafers to be processedare disposed together in the air, the dummy wafers are loaded from thecassette into the apparatus by the same conveyor as the conveyor fortransferring the wafers, at the time of cleaning, and the used dummywafers are returned to their original positions in the cassette. In thisway, a mechanism for conducting exclusively plasma cleaning need not beprovided, and the construction of the apparatus can be simplified. It isnot necessary to handle plasma cleaning as a particular processingsequence, but the plasma cleaning can be incorporated in an ordinaryetching processing and can be carried out efficiently in a series ofoperations.

[0035] The dummy wafers used for plasma cleaning are returned to theiroriginal positions in the cassette placed in the air. Accordingly, theused dummy wafers and the wafers before and after processing do notexist mixedly in the vacuum chamber, so that contamination of wafers dueto dust and remaining gas does not occur unlike conventionalapparatuses.

[0036] The used dummy wafers are returned to their original positions inthe cassette and the numbers of times of their use is managed.Accordingly, it is possible to prevent the confusion of the used dummywafers with the unused dummy wafers and the confusion of the dummywafers having small numbers of times of use with the dummy wafers havinglarge numbers of times of use. For these reasons, the dummy wafers canbe used effectively without any problem when plasma cleaning is carriedout.

[0037] Furthermore, in accordance with the present invention, theapparatus can have a plurality of processing chambers and can transferwafers and dummy wafers by the same conveyor. Since plasma cleaning canbe carried out by managing the timing of cleaning of each processingchamber by the controller, the cleaning cycle can be set arbitrarily,dry cleaning can be carried out without interrupting the flow of theprocessing, the processing can be efficiently made and the productivitycan be improved.

[0038] As described above, according to toe present invention, there areeffects that the construction of the apparatus is simple, the substratesto be processed are free from contamination and the production yield ishigh.

What is claimed is:
 1. An apparatus for transferring substrates,comprising: a first transfer device for transferring a cassette to acassette table, said cassette table being disposed in a vicinity of avacuum processing apparatus and being disposed under a cassettetransferring atmospheric pressure, for placing the transferred cassetteon said cassette table, and for transferring a removed cassette toanother position; and a second transfer device for removing a substratein the cassette, from the cassette, wherein said first transfer devicemaintains a transferring state of said cassette without changing anorientation of the cassette as placed on the cassette table, and saidsecond transfer device maintains a transferring state of the substratein said cassette without changing an orientation of the placedsubstrate.
 2. The apparatus according to claim 1 , wherein said firstand second transfer devices maintain a horizontal plane of saidsubstrate.
 3. The apparatus according to claim 1 , wherein said firsttransfer device transfers the cassette to a position corresponding tothe location of the cassette table.
 4. An apparatus for transferring asemiconductor wafer, comprising: a first transfer device fortransferring a wafer storing structure to a table, said table beingdisposed in the vicinity of a vacuum processing apparatus and beingdisposed under a transferring atmospheric pressure, for placing thetransferred wafer storing structure on said table, and for transferringremoved wafer storing structure to another position; and a secondtransfer device for removing a semiconductor wafer in the wafer storingstructure from the wafer storing structure, wherein said first transferdevice maintains a transferring state of said wafer storing structurewithout changing an orientation of the wafer storing structure as placedon said table, and said second transfer device maintains a transferringstate of the semiconductor wafer in said wafer storing structure withoutchanging an orientation of the placed semiconductor wafer.
 5. Theapparatus according to claim 4 , wherein said first transfer devicetransfers the wafer storing structure to a position corresponding to thelocation of the table.